The electroless plating has been known as the method for giving electric conductivity and metallic luster to a resin material. This electroless plating is the method of chemically reducing metal ions in a solution, and depositing a metal coating on a surface of a material, and with this method, a metal coating can be formed on an insulator such as resins, too, as is different from electroplating of depositing a metal coating by electrolysis with electric power. In addition, electroplating can be carried out on the resin material on which a metal coating has been formed with electroless plating, thereby enlarging the use of the resin material. For these reasons, the eletroless plating has been widely used as the method for giving metallic luster and/or electric conductivity to the resin material for use in various fields such as parts of motor vehicles, household electric appliances, etc.
The plated coating formed with electroless plating, however, has the problems that it takes a considerable time to form the coating, and the adhesion of the coating against the resin material is not sufficient. In order to solve these problems, there has been generally carried out the process of chemically etching the resin material to roughen the surface thereof before electroless plating.
Japanese unexamined patent publication No. Hei 1-092377, for example, discloses the method of previously treating a resin material with an ozone gas, and then electroless plating the treated resin material. In accordance with this publication, unsaturated bonds in the resin material are cut by the ozone gas to be changed to low molecules, and consequently, molecules having different chemical compositions coexist on a surface of the resin material, whereby the smoothness thereof is lost, and the surface is roughened. Accordingly, the coating formed with electroless plating tightly enter the roughened surface to prevent the coating from readily peeling off therefrom.
Furthermore, Japanese unexamined patent publication No. Hei 8-092752 discloses the method of previously roughening polyolefin as a resin material by etching, bringing the roughened polyolefin into contact with an ozone water, and then treating the roughened polyolefin with a solution containing a cationic surface active agent.
In the above-described related methods, the adhesion of the plated coatings is enhanced with a so-called anchor effect by roughening surfaces of the resin materials. With these methods, however, the surface smoothness of the resin material decreases. Accordingly, in order to obtain metallic luster giving good appearance to the resin material, the plated coating must be thick to cause the defect of an increment of the number of man hour.
In addition, in the method of roughening the surface of the resin material by etching, hazardous substances such as chromic acid, sulfuric acid, etc. must be used, and accordingly, there arise problems in the treatment of resultant liquid waste, etc. Furthermore, this method cannot solve the problem that the surface smoothness of the resin material decreases.
Under the above circumstances, Japanese unexamined patent publication No. Hei 10-088361 and Japanese unexamined patent publication No. Hei 8-253869 disclose the method of irradiating a resin material with ultraviolet rays, and treating the obtained resin material with electroless plating. By the ultraviolet irradiation, the surface of the resin material is activated, and active groups on the activated resin material chemically bond to active metal particles as a plating material, thereby forming a plated coating having excellent adhesion.
The method of irradiating ultraviolet rays, however, requires a large amount of energy for activating the surface of the resin material, and accordingly, there occurs the case where the resin material is degenerated with thermic rays from a light source.
Furthermore, it has been difficult to activate the resin material such as polypropylene (PP) or a polymer alloy containing elastomer and PP with only the method of treating with an ozone gas or the method of irradiating ultraviolet rays. In addition, it has been clarified that where the treating time is too short or too long, the adhesive strength of a plated coating lowers, but, the border of the treating time is unclear so that it is difficult to determine the treating time. And the treating time required for effecting a sufficient adhesive strength of the plated coating is generally long, and the productivity is low. Accordingly, it has been desired to shorten the treating time therefor.
The present invention has been made considering these problems of the related methods, and has an object of obtaining the method capable of forming a plated coating exhibiting excellent adhesion by a short pretreatment without roughening a surface of a resin material.
The pretreatment method for an electroless plating material in accordance with the present invention is characterized by an ozone solution-ultraviolet irradiation treating process of irradiating a resin material with ultraviolet rays in the state where the resin material is in contact with a first solution containing ozone being carried out.
It is preferable that an alkali treating process of bringing a second solution which contains an alkaline component into contact with the resin material treated with the ozone solution-ultraviolet irradiation treating process is further carried out. And it is preferable that at least one of an anionic surface active agent and a nonionic surface active agent is further included in the second solution. And it is preferable that the first solution contains a solvent composed of an organic or inorganic polar solvent.
In addition, the method for producing a member having a plated coating in accordance with the present invention is characterized by an ozone solution-ultraviolet irradiation treating process of irradiating a plating material with ultraviolet rays in the state where the resin material is in contact with a first solution containing ozone, and an electroless plating process of subjecting the resin material after the ozone solution-ultraviolet irradiation treating process to electroless plating being included.
It is preferable that an alkali treating process of bringing a second solution which contains an alkaline component into contact with a resin material is further included between the ozone solution-ultraviolet irradiation treating process and the electroless plating process. In addition, it is preferable that at least one of an anionic surface active agent and a nonionic surface active agent is further included in the second solution. And it is preferable that the first solution contains a solvent composed of an organic or inorganic polar solvent. Furthermore, it is preferable that an electroplating process of further subjecting the resin material after the electroless plating process to electroplating is included.